Storing content, such as video, in media which incorporates a NAND flash memory has been widely practiced in recent years. In order to protect the content rights, functionalities to authenticate such media by host devices, such as video players, have been developed. For example, the host devices determine whether the media is an authorized or unauthorized copy and refuses to play the video if the media is the latter. Data required for authentication, such as a secret key, is written to a specific area in the NAND flash memory before shipment. If such data in the specific area can be rewritten by any user, an attacker can erase the area and write data which can pass the authentication to duplicate unauthorized media.